泌阳凹陷页岩储层物理化学性质对井壁稳定性影响的实验研究

Experimental Study on Influence of Physicochemical Properties of Shale Reservoir in Biyang Depression on Borehole Stability

中国南襄盆地泌阳凹陷已探明具有较好的页岩油开采前景。为了完成页岩油的开采,钻井是其中重要的技术环节之一。在钻井过程中,页岩的理化性质将会对井壁的稳定产生直接影响。基于此,在实验室内较为系统地对泌阳凹陷的陆相页岩进行了物理化学性质及其在钻井液浸泡环境中的结构稳定性测试。实验研究发现,泌阳凹陷页岩储层以纹层状或页理状为主,块状构造在岩心统计中仅占15%以内;粒度上,整体以粉砂级以下(<0.062 mm)为主,极少量粉砂级>50%;成分上,粉砂、黏土及碳酸盐矿物三端元含量相对均匀,多集中在20%~40%,三者均无绝对优势。该页岩储层在钻井液滤失量≤5 mL/30 min时,经钻井液浸泡8~10 d即可发生明显的内部水化膨胀,势必在外力碰撞冲磨作用下易发生体积破碎,对造斜段和水平段钻井的井壁稳定带来不利影响,因此在钻井过程中应适当提高机械钻速和降低钻井液的滤失量。

The Biyang Depression in the Nanxiang Basin of China has proven to have good prospects for shale oil exploitation.In order to complete the extraction of shale oil,drilling is one of the important technical links.During the drilling process,the physicochemical properties of the shale will have a direct impact on the stability of the wellbore.Based on this,the physicochemical properties of the continental shale in the Biyang Depression and its structural stability test in the drilling fluid soaking environment were systematically tested.The experimental studies found that the shale reservoirs in the Biyang Depression are dominated by stratigraphic or shale-like structures,and the block-like structures account for only 15%of the core statistics.The granularity is below the silt level(<0.062 mm).In terms of composition,the three-terminal element content of silt,clay and carbonate minerals is relatively uniform,mostly concentrated at 20%to 40%,and none of them has absolute advantages.When the drilling fluid loss is or equal to 5 mL/30 min,the internal hydration expansion will occur obviously after 8~10 days of immersion in the drilling fluid,which is bound to easily break up under the impact of external force.It has an adverse effect on the stability of the shaft wall for drilling in the deflection section and the horizontal section.Therefore,the drilling rate should be appropriately increased and the fluid loss of the drilling fluid should be reduced during the drilling process.